Cellular confinement systems have been used on an increasing basis to resolve difficult engineering problems by enhancing the load bearing capacity, stability, and erosion resistance of materials which are placed within the cells of the systems. Uses of confinement systems have included, for example, supports for structural foundations, road bases, subgrades, and pavement systems. Additionally, cellular confinement systems have been stacked to provide earth and liquid retention structures, such as a stepped back design for hill slope retention. The light weight of, and ability to quickly install, cellular confinement systems have permitted them to be installed in difficult or remote locations where prior building-support techniques would be too expensive or too time consuming.
Cellular confinement systems also protect earth slopes, channels, and hydraulic structures from surface erosion. Grass and other earth slope cover materials have been protected and stabilized through the use of cellular confinement systems. Cells can be infilled with sand, rounded rock, granular soils, aggregates, topsoil, vegetative materials, and other earth materials. Concrete and soil-cement or asphaltic-cement can also be used to infill the cells.
A commercially available cellular confinement system is sold by Presto Products Company (Appleton, Wisconsin) in the form of a plastic-web soil confinement system which is made from high-density polyethylene strips joined by ultrasonic seams. The polyethylene strips are joined in a side-by-side relationship at alternating spacings so that the resulting web section has a honeycomb-like appearance with sinusoidal or undulant shaped cells when the strips are stretched out in a direction perpendicular to the faces of the strips. The sections are lightweight and shipped in their collapsed form for ease in handling and installation.
One challenge associated with the use of cellular confinement systems is that the fill material and the webs may be displaced during installation and long-term operation. Erosion below the web material may cause concrete infill to drop out of the cells. Applied forces such as hydraulic uplift and ice action may lift the web material or lift the fill material out of the cells. Translational movement of the webs may also occur in channel lining applications, or when installing on steep slopes.
In an effort to overcome these problems, "J-hooks", sometimes made from bent steel reinforcement rod or steel rod, have been intermittently spaced along the face of some cell walls and driven into the ground to anchor the web materials before the cells are infilled. The rounded portions of the J-hooks extend over the tops of the cell walls to limit displacement of the web material. While this approach limits displacement of the web materials in some applications, it has not been completely successful in preventing movement of the webs and can leave a portion of the J-hooks extending above the web material.
Another approach involves the use of reinforcing members positioned within a hole in the web material, as indicated in U.S. Pat. No. 5,449,543 to Bach et al. While this approach has shown success at preventing such movement, securing the reinforcing members to the web and to the ground has posed a problem. With the reinforcing member implemented as a flexible tendon, the tendon is usually secured to the web by a knot, a washer, or a loop around a segment of PVC pipe. The tendon is often also secured to a segment of steel reinforcing bar driven into the ground. To secure a tendon to the reinforcing bar, the bar is typically bent on the top end to create a hook. The task of bending the hook into the reinforcing rod can be both time consuming and expensive. Further, forming the hook sometimes requires heating the end of the reinforcement rod before attempting to bend it. For certain applications, this task must be done at the job site, and it can be difficult to find contractors capable of performing the work.
The use of bent reinforcing rods can also result in utilization of a larger quantity of reinforcing rod than is desirable. The entire hook is made out of reinforcing rod, and therefore roughly six inches of rod is often used to create the hook. This six inch portion of rod requires an additional expense.
Other problems associated with using bent reinforcing rods is that they typically have a small "striking surface" for driving the rod into the ground and the striking surface may not be perfectly centered above the shaft of the rod, resulting in the rod shaft bending when the shaft hits an obstruction, such as a rock. The off-center striking surface also makes driving the rod straight down more difficult.
Consequently, a need exists for a fastener for a cellular confinement system which overcomes the aforementioned shortcomings associated with existing fasteners.